Double-wires plus arc additive manufacturing(D-WAAM) system for Al-Cu-Mg alloy using variable polarity gas tungsten arc welding(VP-GTAW) process was established. Al-6.3Cu and Al-5Mg wires were employed as filling metal, the microstructure and mechanical properties of as-deposited D-WAAM samples were analyzed. Experimental results show that the excellent deposits wall samples can be achieved and the deposition efficiency can be improved by using D-WAAM process. Al-Cu-Mg alloys with different element content of copper and magnesium were obtained by adjusting the two wire feed speed. The microstructures of Al-Cu-Mg deposits were mainly composed of columnar dendrite and equiaxed dentrite grains with the non-uniformly distribution characteristics. Mechanical properties can be enhanced due to the addition of alloying of element magnesium. The microhardness of as-deposited Al-Cu-Mg alloy was 90-100 HV. The UTS, YS and elongation of as-deposited D-WAAM alloy can be increased to 286 MPa, 183 MPa and 4.5%, respectively.